Posted
by
timothy
on Friday November 13, 2009 @08:09AM
from the they-don't-even-make-good-nightclubs dept.

astroengine writes "Physicists are getting excited about the possibility of micro-black holes (MBH) being produced by the LHC and an international group of researchers have done the math to see what kind of impact they could have on the Earth. Unfortunately, if you're a megalomaniac looking for your next globe-eating weapon, you can scrub MBHs off your WMD list. If a speedy MBH is produced, flying through our planet, it will only have a few seconds to accrete the mass of a few atoms. It would then be lost to space where it will evaporate. If a slow MBH is produced, dropping into the Earth where it sits for a few billion years, the results are even more boring."

To do this they need to hit each other first. Their cross section is tiny (10^-35m, size of an electron is 16^-15m), they will be moving slowly (about 11km/second if they are created with zero velocity at CERN) - so the chance of them hitting each other is small. If they came across an atom - most of that is empty space; the protons & neutrons are mostly empty space (between the quarks) to something as small as the black hole.

Not disagreeing with you generally of course - but aren't protons & neutrons more accuratelly conceptualised as, indeed, a sphere with each of the quarks not occupying any specific point but being "mixed" together?

Yeah, but those are the same people who think aliens are traveling across the vast distances of interstellar space to play ass-grab with rednecks in trailer parks. You have about as much chance of educating the unwashed masses as you do of convincing them to become washed masses. Best to keep sedating them with sports.

Photons pop out of the vacuum all the time. A photon and an anti-photon (or do they call it a virtual photon) will appear at the same time, and as long as the pair doesn't stick around longer than the mass * Plank's constant, conservation of mass is preserved.

If the photon and anti-photon appear at the edge of a black hole, sometimes the photon goes off, and the anti-photon gets sucked into the black hole where it cancels some of the mass of the black hole. Thus it looks like the BH is radiating and evaporating, but nothing actual leaves the BH.

Physical insight on the process may be gained by imagining that particle-antiparticle radiation is emitted from just beyond the event horizon. This radiation does not come directly from the black hole itself, but rather is a result of virtual particles being "boosted" by the black hole's gravitation into becoming real particles.

A slightly more precise, but still much simplified, view of the process is that vacuum fluctuations cause a particle-antiparticle pair to appear close to the event horizon of a black hole. One of the pair falls into the black hole whilst the other escapes. In order to preserve total energy, the particle that fell into the black hole must have had a negative energy (with respect to an observer far away from the black hole). By this process, the black hole loses mass, and, to an outside observer, it would appear that the black hole has just emitted a particle. In reality, the process is a quantum tunneling effect, whereby particle-antiparticle pairs will form from the vacuum, and one will tunnel outside the event horizon.

I'm not exactly sure how 'preserving total energy' works in this context, but I think I'll trust Hawking on that one.

There's no such thing as an anti-photon. In the case you are describing - pair production - both of the particles are virtual particles. They can be an electron and a positron (anti-electron), a quark and its anti-quark, etc - any particle/antiparticle pair. However a photon is its own anti-particle.
And your explanation of the uncertainly principle is wrong. The time-energy formulation says
(uncertainty in time) * (uncertainty in energy) = hbar,
so the time limit for the life of the virtual particles is Planck's constant / energy
(or Planck's constant divided by mass, since mass and energy are proportional and we measure the mass of these particles in units of electron-volts anyhow).
Note that if it's mass * hbar, as you have above, then the higher the mass is, the longer the particles can stick around! That's exactly backwards. It's the tiny little particles that are flickering in and out of existence, not huge massive objects! If it were mass*hbar, you'd have virtual planets, stars and galaxies - the larger the object the more likely it would be to suddenly
appear out of nowhere! This is an amusing thought but doesn't accurately describe the reality that we find ourselves living in.

There's no such thing as an anti-photon. In the case you are describing - pair production - both of the particles are virtual particles. They can be an electron and a positron (anti-electron), a quark and its anti-quark, etc - any particle/antiparticle pair. However a photon is its own anti-particle. (See http://en.wikipedia.org/wiki/Antiparticle [wikipedia.org] )
And your explanation of the uncertainly principle is wrong. The time-energy formulation says
(uncertainty in time) * (uncertainty in energy) = hbar,
so the

The thing I'd add to that is that there are no anti-photons -- photons are their own anti-particle.

That's correct, but something I've never wrapped my mind around. When the photon and photon-prime are created, then one falls into the black hole, how does the BH know that its photon should cancel mass, rather than increase it?

Pairs of particles (one matter, one antimatter) form randomly near the event horizon. One quantum-tunnels out of the black-hole and so appears to an observer outside the black-hole to have been emitted. Therefore, to conserve energy, the other particle must have negative energy and thus the black-hole loses a tiny parcel of energy (and thus mass).

The main point is that, because the particle was formed near the event horizon and didn't come from the black-hole itself, it carries no information out - thus, while the black-hole loses mass, no information can escape.

Where does water evaporate to? Black hole evaporation is not quite the same; it's the release of Hawking radiation, rather than the release of gaseous water molecules, but it's the same general idea. The substance of the black hole is converted (slowly) into radiation and escapes. Because energy is just a much less dense version of matter, this means that the black hole loses mass until eventually it doesn't have enough left to remain a black hole. There's no magic or mystery any more than there is in t

Photons pop out of the vacuum all the time. A photon and an anti-photon (or do they call it a virtual photon) will appear at the same time, and as long as the pair doesn't stick around longer than the mass * Plank's constant, conservation of mass is preserved.

If the photon and anti-photon appear at the edge of a black hole, sometimes the photon goes off, and the anti-photon gets sucked into the black hole where it cancels some of the mass of the black hole. Thus it looks like the BH is radiating and ev

Well, the key isn't just mass, but also radius. Gravity (I'll go newtonian, just because I'm lazy) increased linearly with mass, but decreases with the square of the radius. So for example, if you packed something the mass of Earth in just half the size of Earth, the gravity on the surface would be 4 times that of Earth. Squeeze it into a quarter of the size of Earth and get 16 times the gravity on the surface. Squeeze it small enough and you have a black hole.

If you do the proper maths, the Schwarzschild radius of a black hole with the mass of Earth is about 9mm.

Which really means, don't think something that will suck matter and bend light spectacularly all the way to Alpha Centauri. It means that if light happens to go within 9mm of that singularity, it ain't coming out. But farther away, it's still a body with the mass of Earth. The moon's orbit will still have the same radius for example.

Ok, so what would happen if one of these super-mini black holes were to, say, have matter thrown at them from opposite directions at close to the speed of light, with the equivalent energy of a family car hitting an immovable object at 1000MPH? Would that potentially cause it to grow?

Well, yes, any matter you throw at it (and energy converts neatly to matter too) can only cause it to grow. But there's still the problem of how much and how close.

But, really, let's do some simple maths.

Let's say we want to produce a black hole the size of a helium atom. You know, big enough to occasionally actually bounce into stuff and gobble it up. (Remember, only matter coming closer than the Schwarzschild radius is actually gobbled up.) It's not a big black hole, but it has the potential to grow. So we apply:

r = (2G/c^2) * m... Where the thing in brackets is approx 1.5 * 10^-27 m/kg. We'll want to get a hole measuring 3x10^-11 m. So we'd need a mass of 2x10^15 kg, or two millions of millions of metric tons.

Yep, that huge a mass will only gobble stuff up if it comes within 3x10^-11m of it. But it's a start, and as an evil genius you may have to start small;)

To produce that hole, the protons we throw at it, as a total, will have to have the equivalent of that much mass in energy.

Let's transform that into MeV though, since we are talking energy. 1MeV is about 1.8x10^-36 Kg. Let's round to 2x10^-36, since we're only doing a back-of-the-napkin calculation, and are only interested in rough ballpark figures. So we're talking about 10^51 MeV

If we got that energy from uranium, and assuming that we could (A) split every single U235 atom, and (B) capture 100% of the released energy, each atom split releases 180 MeV. (RL reactors don't come even close in both aspects.) Again, let's round it up to 200. (In my fantasy land, reactors are better than 100% efficient;)

That works out to about 5*10^48 uranium atoms split. Avogadro's number being about 6x10^23, that's about 10^25 moles of uranium. (Again, I'm only interested in the order of magnitude. Plus, we rounded up in the other direction before, so it evens up.) And a mole of U235 weighs 235 grams, or about half a pound or almost a quarter kilo.

We're talking about 2 to 3 times 10^24 kilos of uranium, or 2 to 3 times 10^21 _tons_ of U235. That's 2-3 thousand billions of billions of tons of U235. Or about a hundred thousands of billions of billions of reactor-grade enriched uranium. Completely used up in a 100% effective reactor.

So basically yes we _could_ make a bigger black hole by keeping throwing stuff at it, close to the speed of light, but the energy requirements are nuts even to get a hole the size of a helium atom. We don't even _have_ the kind of reactors and capacitors where you could split a hundred thousands of billions of billions of reactor-grade uranium and dump it all into just creating a black hole.

You seem to know your physics. I have a question.
If a "stationary" black hole gets hit by an object of comparable mass, and neglecting the effects of gravity between both objects, will the black hole move at all? Will it only get as much kinetic energy as the mass it absorbs had, none at all, or you could actually hit it?

This is actually quite easy to answer, because momentum is conserved (in both Newtonian physics and General Relativity). In the Newtonian model, which is accurate for the masses and velocities we're dealing with, momentum equals mass times velocity. A stationary black hole has mass m_0 > 0 and velocity v_0 = 0, for a momentum of m_0*v_0 = 0. An incoming object with mass equal to the black hole has mass m_1 = m_0 and velocity v_1 > 0, for a momentum of m_1*v_1 > 0. The joint system, after the bl

you'd have to figure out a way to suspend it inside your spaceship and travel along with your spaceship.. which would have to be spherical because different gravitational magnitudes being exerted on different parts of your body has got to be uncomfortable.

Even with it being spherical, your feet would get a noticeably larger gravitational force than your head.. blood circulation might become an issue. Somebody with too much time on their hands could probably work out the 'safe' minimal radius of the sphere surface you'd be walking on.

If you've got a singularity (worst case in our example) that's the mass of the earth, how's that supposed to stop any light/matter/etc escaping? It's not massive enough!

A singularity with one Earth mass will be _tiny_. That means light and matter can get so close to it that they won't be able to escape. Of course, if you're one Earth radius away from it, it'll just exert as much gravitational pull as the real Earth.

substitute massive for dense. BH are dense objects, but they don't need to be massive. As long as you squeeze enough mass in a tiny enough place - hence the theoretical possibility of MBH forming - you have a black hole (pardon me if I oversimplified this).

Well lets think for a 2D black hole. As 3d Ones are hard to picture in your head. So Imagine a plane of streachy rubber. That will represent normal space time. Then you take 2 objects say a bowling ball and a pin needle. You put the bowling ball down its massive weight has distored space time and made a large hole where an object say Rowling a marble across the plain when approaching the bowling ball would fall in the well. Next you take a pin needle you create a very small hole with the same angles as t

In principle, any mass, if packed densely enough, could become a black hole. For each mass - from a cluster of atoms to an entire galaxy - there is a calculable quantity called the Schwarzschild radius [wikipedia.org]. If you could somehow pack the mass so that it fit inside a volume smaller than that mass's Schwarzschild radius, the force of gravity would invariably overcome all other forces and cause the mass to become a singularity. The Schwarzschild radius also defines the "edge" of the black hole - if anything, including light, gets closer than one Schwarzschild radius from the central mass, it will not be able to escape. In other words, at the Schwarzschild radius, the escape velocity [wikipedia.org] is the speed of light.

It is easy to see how the core of a really big star could collapse on itself in a supernova - there's just so much mass, coupled with the force of the explosion. However, our own sun could become a black hole - if some as-yet unknown physical process could squeeze its entire mass into a 6-km diameter sphere. The Schwarzschild radius of one solar mass is about 3 km.

It is important to note that, were this to happen tomorrow, the Earth and the other planets would continue to orbit the black hole sun exactly as they have done for billions of years. The gravity of the sun hasn't changed, because its mass hasn't changed. If you were, however, unfortunate enough to come within 3 km of the center of the black hole sun, that's the last the universe would ever see of you. (As a practical matter, you'd be doomed long before then, simply because no rocket would be powerful enough to bring you away once you got closer than a few thousand kilometers. To escape the black hole sun once you were, say, 3.1 km away, you would need to somehow achieve a speed near to the speed of light, which we simply can't do.)

It is also important to note that you would not be sucked into a black hole if you came within 3 km of the center of the sun as it exists today, shining hot and bright. This is because 99.999% of the mass of the sun lies outside of that 3 km radius and so "doesn't count" in terms of the force of gravity. Aside from instantly transforming into plasma from the heat, you would actually feel far less gravity than you would on the Moon. (For reasons why, see here [wikipedia.org].) Remember: a black hole would exist only if you could compress the whole mass of the sun into that 3-km radius spherical volume.
This can be applied to just about any mass. The Schwarzschild radius of the Earth is about 9 mm - smaller than a grape. This gives you a sense of how densely you'd have to pack things if you wanted to make an Earth-mass black hole. For a pair of protons smashed together at high energies - as in the LHC - I think you need to bring in other areas of physics than just general relativity. Suffice to say the Schwarzschild radius would be much, much, much smaller than the size of a proton, which in turn is much, much, much smaller than the size of an atom, which is much smaller than the distance between atoms in most solids. So in order for a micro-black-hole to accumulate mass, it would need to pass very close, on the order of its Schwarzschild radius, to the nucleus of another atom. At the length scales we are talking about, that's about as likely as me randomly shooting off a bb gun and hitting a passing bird a kilometer away.

So rest easy, the world isn't about to end.

I apologize for the long answer, but I hope it has answered your question.

A black hole is any body tightly packed enough that its escape velocity is greater than the speed of light. Because material, as a result of this, can ONLY travel towards the centre of mass (outward travel, sideways travel and staying stationary are all forbidden this therefore HAS to form a singularity, as matter is all forced to head towards and occupy a single point.

The distance from the object where the escape velocity drops below the speed of light is the event horizon (aka the Schwarzschild radius), within this sphere* no light can escape so we call this sphere the black hole. In the centre of it is the singularity, which is the "true" black-hole.

All objects have Schwarzschild radii, however this radius is only a "real" radius if it exceeds the radius of the object. Wikipedia claims the Schwarzschild radius of the Earth is 9mm, so Earth would form a black-hole itself if it were compressed to smaller than 9mm in radius.

The key point is that a "black-hole" is not an object, per se, but a region of space from which light cannot escape. The "object" would be the singularity in the centre. From outside the black-hole, there's no real difference from a star of the same mass in terms of gravity.

*rotating black holes have a slightly different shape, depends on the speed of rotation.

Black-holes are not a source of energy (excluding the monumentally tiny energy output via Hawking radiation), any energy gained harnessing black-holes would be from the accretion disk around them in which particles accelerating towards the black-hole emit radiation due to friction among themselves. However, you'd likely need a stellar-mass black-hole to get a realistic accretion disk going.

Anyway, ZPMs aren't hard to find, you just need Ancient-built replicator civilisations or time travel.

Am I the only one who reads MBH as mega black hole, not micro black hole? It's confusing.
If the prefix is micro, it would make sense to use a letter that actually means micro, instead of a letter that represents mega.

It is somewhat confusing, I agree, as the greek letter "mu" normally represents micro, and "SMBH" is the normal acronym for Super Massive Black Hole (black holes at the centres of galaxies that weigh millions of times the mass of the sun).

TFA calculates the likely results based on higher dimensional brane physics. It was done earlier in more classical relativity maths and the results summarized in Alan Boyle's Cosmic Log. The max mass was greater and thus life time longer. Still, mass and accretion never crossed the limit that would allow it to reach whatever they call critical mass for these thing. The example given was that if it were charged and it were trapped within the electron cloud of an atom (both conditions lending it additional life span), it would circulate there on the order of weeks before encountering an electron which it could then consume. Even if it did so it would evaporate before it could hit the run away point, and would likely evaporate before eating even one electron. The specific results were different but the conclusion the same - too small to live long enough to do any damage.

Another point made in Cosmic Log (I don't recall if it was the same person/calculations) was that quantum black holes (a more correct descriptor than 'mini-') of the mass and life span hypothesized would be likely to occur regularly in the atmosphere due to incoming primary cosmic rays. Those have been impacting the Earth for billions of years, and we're still here. The hypothesized Hawking radiation is not obvious, thus these may not even be occurring. In any case, their creation would be a highly improbable event.

That last assertion is strictly conjecture based on calculations by my Brambleweeny 57 sub-meson brain. Now if you'll excuse me I'm for a nice hot cup of tea.

I think the LHC has destroyed the world multiple times now. It is just that we here and now are the survivors of the disasters....

According to the Multi-verse theory, each quantum fluctuation creates a new universe or timeline.....

Because we are alive and well and not consumed by a black hole, that means in "our" branch of the multiverse we haven't created a Black Hole that swallows earth "yet".....

But fear not because Even if the LHC were to create a earth consuming black hole, strangelet, way to lower the energy level entire universe leading to it's immediate destruction. We will survive because at least one branch of timeline will survive by failing to create these anomolies and go on to branch out some more to survive whatever weird physics experiments we dream up of go arwy.....

The only problem is when creating black hols and exotic matter that is large enough to reduce quantum probability and then we are really screwed.

"Calculating how quickly a micro-black-hole would accumulate mass strikes me as a great undergrad tutorial question."

Which implies using existing theories to calculate it. What I think the grand parent post is saying is that we don't know for sure our current theories are all correct. After all, if we knew it all 100% correctly, there wouldn't be any need to build the LHC.

Scientific evidence accumulates over time. In science, its extremely hard to say 100% correct and be very careful of anyone who claims different.

Our current theories are our best current understanding of the universe and they do indeed work well. But we cannot be 100% sure. In the case of creating a black hole we won't know for sure until we create one under the conditions in the LHC (which due to the grouping of particle collisions in the LHC is different from a single high speed collision happening in the upper atmosphere).

Throughout the history of science we can see time and time again where theories were overturned. We therefore cannot assume all our current theories are correct under all possible conditions. There could be factors we are so far ignoring.

The problem is, the creation of a black hole in the LHC is kind of a unique experiment, as most wrong answers in science don't have such horrific results if our current theories are wrong.

I'm not so sure. The behavior of electrons is not well-known: it's not even certain whether they have internal structure or not. However their behavior in an electric circuit is well-described by very old physics. Likewise the formation and evaporation of micro-black-holes is not very well theorised, however their essential and most threatening property - their gravitational attraction - is very well-defined, even at masses as low as those of protons. Whether these black holes would mass less than that, I d

The problem with this whole situation is that I can't verify it myself in the next couple of days. I do not have the skills or foundational knowledge. The problem with this whole thing is that these scientists are asking 99.9999% of the public to trust them,w e won't get you killed by a black hole. We can't tell if they are worthy of that much trust. Maybe their calculations are tinged by self interest or tinged by interest in the the possible scientific discovery

However, even basic physics should be enough to determine that microscopic black holes aren't going to be particularly dangerous. The kind of black holes that could be created by the LHC have a very small mass - they're created by smashing a couple of subatomic particles into each other, after all. The total mass of the black hole can not possibly be higher than the total mass of the particles that created it.

That means that the black hole will have the same gravitational force as the particles that created it. Therefore, the event horizon of the black hole will be very small. Since matter is composed mostly of empty space, the chances of it actually hitting anything are remote, to say the least. In order for it to absorb a particle, it would have to almost collide with it. This is very unlikely, although given enough time probably will happen.

Worst case scenario - Hawking radiation doesn't exist. The micro black holes will continue to exist indefinitely, and will slowly consume the planet. Before the micro black hole has absorbed even a few kilograms of matter, the Sun will expand, swallowing the planet. The black holes will continue gradually consuming the Sun, and given a few quadrillion years or so (and the entire universe will be long dead by that point) might actually start to do some damage. By this point, I doubt that any humans will still be around to care. If we've managed to survive the destruction of our own planet, the death of our own star, and the death of the universe itself, a puny little black hole shouldn't be a problem.

More likely scenario - Hawking radiation does exist, and the micro black holes will simply evaporate before they even come close to absorbing anything else. No big deal. If we detect evidence of Hawking radiation, that pretty much confirms the existence of black holes, and Steven Hawking gets a Nobel prize.

This is a typical nonsense argument. You imply that because there are some things we don't know (e.g., questions to be answered by the LHC) that it's reasonably possible that we will encounter aberrant behavior that contradicts previous observation.

There are few avenues for the MBH to be incorrect. They already assume that we are wrong about Hawking radiation (otherwise an MBH would boil off immediately). The only real options are that energy conservation is violated and the LHC is able to somehow create a

which due to the grouping of particle collisions in the LHC is different from a single high speed collision happening in the upper atmosphere

This statement makes no sense. The quarks have no clue if they're in the atmosphere or the LHC.

The ignorant, murderous assholes who have been making a living for themselves inducing panic in people by waving their hands about LHC black holes have been making much of this "we don't know everything" rhetoric. But unlike the scientists who have performed these actual ca

Which implies using existing theories to calculate it. What I think the grand parent post is saying is that we don't know for sure our current theories are all correct. After all, if we knew it all 100% correctly, there wouldn't be any need to build the LHC.

This line of logic is ridiculous. We're building the LHC to explore many things, one of which is probing a few plausible alternate theories that predict black hole production at a measurable rate. But the assumption that that means we can't come up with logically-consistent explanations of how such a black-hole would behave is ridiculous. You can put some bounds on it, right? You can say that a black hole won't make bunnies leap out of the wall. Not because it *sounds* ridiculous, but because there's no mathematically and logically internally consistent theory under which such a thing could happen. You can keep moving this line until you start finding regimes of behavior that might be consistent with new theories allowed, compatible with previous observations but allowing new ones under these new conditions. And that's what theorists are doing!

Any claim of unexpected behavior without a plausible and mathematically self-consistent theory to back it up is baseless. Which isn't to say one doesn't exist (the whole absence of evidence thing), but until one does, there's just as much sense to prepare for the coming bunny invasion.

How do we know with certainty how a black hole behaves? It would seem to me that studying something from millions of light years away where we only get indirect evidence is not the same of plunking one down in the middle of the earth and experiencing it firsthand.

Interesting. I wasn't aware that this was the case. Can you point me to any good discussions on studies on these black holes or even if they have truly been detected. Wikipedia seems to indicate that they are only theoretical...

The argument goes like this: There are plenty of cosmic rays which impact our atmosphere, the other planets in the solar system, the sun, other stars, everything, with energies across a huge spectrum, including LHC energies. Either the LHC will produce MBH or it will not. If it will, then cosmic rays also produce MBH, and do so without destroying any of the things we can see in the sky, so MBH from the LHC would similarly not destroy the earth. If the LHC will not produce MBH, then we have nothing to worry about in that regard anyway.

This argument works for just about any Earth destroying LHC scenario, except, I suppose, the time traveling killer Higgs;)

We know how a black hole behaves by working with the theory. Essentially, a black hole can be modeled as a particle with large mass and possibly some charge and/or spin. It has no other definable qualities. Plug a particle like that into your equations and it's not difficult to calculate its behavior.

Of course, physicists are known for making models that are simplified to the point of absurdity. Have you heard the story of the model that assumed massless, spherical cows?

Ah, the fear of the unknown. Yes, a classic. "I don't understand it, and I don't believe that they do either".

I've got news for you; this is as good (or should i say precise) model of these things as you are going to get right now. It's the cutting edge of our understanding of how MBHs work, and _that_ understanding in turn depends on a quite large, quite solid foundation of math and physics.

It's the cutting edge of our understanding of how MBHs work, and _that_ understanding in turn depends on a quite large, quite solid foundation of math and physics.

So please, this isn't speculation, it's SCIENCE.

I thought science is when you confirm your theories by experimentation. I didn't know we've had the chance to confirm the precise mechanics of black holes via experimental observation.

At that stage, calling it "solid foundation" and deflecting doubts sounds to me more like religion, and not science.

The main lesson of science is to be humble, all scientific models are "incorrect" in the long term. While I don't find the LHC is a threat, the outcome of its tests will very likely surprise both sides of thi

I thought science is when you confirm your theories by experimentation.

Science is the interplay between theory and experiment. Developing fields don't have to rigidly follow the hypothesis->experiment->modification->hypothesis->etc. model or risk being rejected as unscientific. Theoreticians and researchers can make valuable advances on untested theoretical work or unexplained experimental results to try to fill out new, poorly understood areas. The popular perception that science must evolve according to rigid principles is simply false. Like any other discipline

The main lesson of science is to be humble, all scientific models are "incorrect" in the long term.

But they're not *equally* incorrect. They're as good as they are useful at modeling the world around us in their particular regimes.

We don't put Newton by the wayside just because we know about GR. And likewise if GR is ever expanded on or replaced, we still might use it to correct the time-slew of GPS satellites. It's about the best tool available for the job. And right now, the best tool for making decisions about the behavior of black holes and high-energy interactions based on the evidence availa

In this case it's quite different. It's not religious zealots crying wolf at something they don't understand. It's rational people, some of them scientists, saying that we really don't know for sure, that our current knowledge could be flawed. A real scientist should always be ready to question our current knowledge.

Another way to put it: if we were so sure that what we know is 100% correct then we wouldn't need to build the LHC to test our theories in the first place.

Another way to put it: if we were so sure that what we know is 100% correct then we wouldn't need to build the LHC to test our theories in the first place.

There's a nice equivocation in this statement: we can be as sure as we are of anything that LHC black holes won't destroy the Earth. If they did we'd see evidence in the cosmic-ray spectrum due to evaporating black hole signatures and the like, as well as the Earth not actually being here because it would have been destroyed in the past.

I've got news for you; this is as good (or should i say precise) model of these things as you are going to get right now. It's the cutting edge of our understanding of how MBHs work, and _that_ understanding in turn depends on a quite large, quite solid foundation of math, physics and observations.

It could be wrong, but it can only be wrong in one direction. The kind of collision that the LHC is going to be producing happens all the time in the upper atmosphere as cosmic rays hit. There are three possibilities:

The theory is approximately correct.

Micro black holes aren't formed at all at this energy level.

Micro black holes evaporate much faster than expected (unlikely, because this would produce more radiation than we observe).

The math that suggests that a quantum black hole will evaporate in an instant may be fairly advanced, but the math showing that even if Hawking is completely wrong such a black hole would have no noticeable effect on the earth over a 13 billion year period is not all that advanced.

Then there's simple logic. While LHC may produce the most powerful collisions ever under our control, nature routinely produces much more powerful collisions including cosmic rays. Clearly, in billions of years none of this has resulted in a planet eating black hole.

Our planet is small and not particularly dense. There's only one, and something like MBH or strangelets could be fairly rare. We could be lucky.

Fortunately, there's an enormous field of stars, including large, dense neutron stars. Neutron stars are great at capturing errant particles, producing MBHes, and things like that. Looking at our estimates of the ages of these neutron stars, you can show that micro black holes cannot be responsible for stellar/plane

The problem is, there is cause for real concern. Maybe not with the LHC but with science in general. 1. The universe is vast, and old. It's quite clear that, if life is as common as we think it is, the universe should be filled with ancient civilizations. 2. We have no evidence of any alien life... where are they? 3. We have a very rudimentary understanding of physics. 4. It may very well be that it is common for civilizations to evolve to the point at which we are at but then mistakenly destroy themselves

To answer point 2, current evidence is that human radio signals will be distorted by the heliopause at the edge of the solar system such that they are undetectable from outside. Therefore, an incredibly strong and likely custom-built communication system would be needed to penetrate deep space and be detectable by aliens.

Secondly, while the Universe might be vast, we can only really stand a chance of picking up signals from within the Milky Way (and even then only fairly nearby, excluding stupendously power

It should be relatively trivial for an advanced civilization to seed every star in the galaxy with self replicating probes. The initial investment would be only enough to construct the first generation and send them out, after that they would reproduce with local resources and send out the next wave. The apparent lack of such probes in our solar system should be, in my opinion, much more concerning to the SETI crowd than the lack of radio transmis

It's perfectly possible to pack matter into it's own Schwartzchild radius, that is the radius at which the escape velocity from the collective body is greater than the speed of light. Once the escape velocity is greater than the speed of light, nothing can escape and so a black-hole is by definition formed.

If you're really interested, you really need to study General Relativity to properly prove the plausibility of their existence.

The existence of a Schwartzchild radius assumes that gravity can ever be stronger than the repulsive forces within the nucleus. It cannot. Both increase simultaneously as you increase mass. Gravity's attractive force will never be stronger than the electrostatic forces that hold the particles apart.

To clarify that: because the attractive and repulsive forces scale simultaneously, and because the repulsive forces will always be much larger than the attractive forces, it is impossible to pack any amount of matter within its own Schwartzchild radius.

On small scales, that is true. However, take the moon. Electromagnetically it's neutral, however it exerts a sizeable gravitational pull. As the Schwartzchild radius is proportional to mass (not mass squared or cubed, but mass), if one took instead 8 moons and packed them together in a cuboid arrangement, the mass has increased eight-fold while the radius has only doubled. Therefore if we keep adding mass, there will come a point when the Scwarzschild radius is larger than the radius of the huge moon-array and therefore the whole moon-array has an escape velocity greater than the speed of light and is therefore a black-hole.

Now imagine if all those moons are positively charged - it still doesn't matter, because no matter the strength of the outward force it cannot give them a velocity greater than that of the speed of light, so they remain a black-hole.

Gravity is so significant on large scales precisely because of this - with no negative charge, gravity is the most significant force at large distance scales.

No, they are units of acceleration, m/s^2. My point was that it is impossible for a finite gravitational field to accelerate anything to the speed of light. Not that the field itself equaled the speed of light, but that the field integrated over some finite time supposedly equaled the speed of light, which is impossible for any finite field.

Short answer: because the escape velocity is greater than the speed of light inside the Schwartzschild radius, matter cannot travel outwards, but also cannot stay stationary (to prove this properly you need some fairly complex general relativity). Because of this it can only head towards the centre of mass, so the matter all converges on a single point. As the escape velocity only increases as one gets closer to the centre, this forces all the matter into a single point of spacetime, the singularity.

Gravity is much, much weaker than the subatomic electrostatic forces that hold subatomic particles apart.

It really isn't, not in the way that you mean. Yes the Gravitational Constant is much smaller than Coulomb's Constant, and yes the gravitational attraction between two protons is much weaker than the electrostatic repulsion between two protons.

However as soon as you do anything more complicated than compare two charged particles, things change. The reason is because the two forces bind to different pro